pushing coolant out

[aussie merc]

OK here's one for those with experience cause im out of ideas. we have a 59A in a 39 mercury , Take it for an hours run and it pushes coolant out overflows the catch tank capacity of 1 liter [1 quart]. temp stays within range 180/160 deg F . Has 160 thermostats. Have carried out the following tests 1 comp test all cylinders with 5% . 2 tested coolant for exhaust traces result nil . 3 no signs of coolant at oil filler breather [ white slime] .4 oil sampled and tested again no trace of coolant . 5 pressure tested system A, when running no pusle on gauge that would indicate compression leak when running B pressurized system to 12 psi and left o'night still had 11psi in morning .C , tested cap cracks open at 7.5 psi and resets at 6 psi . Both exhaust pipes do drop condensation when starting but any trace disappears after 10 minuets ,have caught this in baking pans and again no trace of coolant . GO FIGIURE any ideas welcome thanks

[Steves46]

Are you running a stock radiator? If so, the pressure cap should be 4 lbs. Anything greater can cause problems.

[40cpe]

Just curious, does it pull the coolant back into the radiator as it cools off?

[paul2748]

Ar you filling it too full ? Water need room to expand

[Lawson Cox]

Plugged radiator?

[aussie merc]

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P.S. living in Sydney Australia temp range average is 25F /95F

[Flathead Fever]

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A 4 lb cap is the maximum pressure on an Early Ford radiator. In the 1980s at work we had an old-timer that was doing our radiators at work. I had ordered a radiator from the Brass Works for one of my cars, and I asked them why the original radiators were only good to 4 lbs and he said it was because the tanks brass was thinner. I was pretty sure that wasn't correct. I asked our old-time radiator guy. He said, it had nothing to with the tanks thickness it was the width of the solder joints. The solder joints are not as wide as modern radiators and cannot handle the pressure.

It sounds like you have performed every test there is. This is a pretty common complaint people with old Fords have. If it is an original radiator, the top tank has a built-in space for coolant expansion. If you fill it to the top when it is cold, it will puke out the overflow when it gets hot. Most people panic and refill the radiator to the top again and the cycle continues to repeat. It could be the coolant is expanding more than what your external overflow tank can handle. As long as the engine is not overheating let the coolant level stay at what it is after is has puked out the excess. Once it cools down you can check the radiator's level and then dont fill it higher than that when it is cold. Make sure your radiator cap is one designed for an external overflow tank. They have a valve that allows the water to return to the radiator as the engine cools down. There are two different kinds of caps, one with and one without an overflow tank. If the valve in the cap goes bad you will see the upper hoses collapse as it cools down because the coolant cannot return and creates a negative pressure in the hose.


If this is a modern radiator find out what pressure it is rated for and if will handle it try a 12-15 lb. cap.


When you shut off an engine and air is no longer flowing through the radiator the temperature will rise above normal operating temperature and this is when you usually see them puke out the overflow. If you notice on modern cars with electric fans, when they are shutoff, the fan will continue to run. This prevents that temperature rise after then engine is shutoff.

There are rumors that persist to this day, that installing restrictors or cutting off every other impeller on the water pumps will help them cool. If this was true, I'm, pretty sure Ford would have figured that out. That modification had nothing to do with cooling. It was done on race cars because at continuous high rpms, and two water pumps pumping away, like on a dirt track jalopy the water circulated faster than it could fall through the radiator, and it would push water out the overflow. So, the racers slowed the coolant flow down with restrictors of water pump impeller modifications. On the street, you want the maximum flow through the radiator as it can handle.

[aussie merc]

Yes it does pull the coolant back in but how much should the system expand when hot as it overflows when hot yet empties the bottle when it cools and no i don't think the rad is blocked internally or externally as when the coolant level is correct it runs at required temps and during winter is no problem but as we approach summer it becomes a nightmare

[fordyford]

FLATHEAD FEAVER is correct. It sounds like a normal system with too much coolant in the system.

[Brian]

You have no problem. As the coolant heats up it expands, going into your catchcan. As it cools it syphons back into the radiator. The radiator is always full, irrespective of coolant temperature.

[aussie merc]

OK but how big a catch tank is required because its obvious the current one is to small

[cadillac512]

A commonly used figure for expansion of coolant is 6%. In a 20 qt system that will be 1.2 qts, so a 2 qt tank would be a good size to use.


One other thought...Have you considered removing the tank and using an original type cap with the radiator filled to just over the cores when cold? That almost always works well if the radiator is correct and in good condition, and it seems yours is since it cools well.



Terry

[Gene1949]

Originally Posted by cadillac512

A commonly used figure for expansion of coolant is 6%. In a 20 qt system that will be 1.2 qts, so a 2 qt tank would be a good size to use.
One other thought...Have you considered removing the tank and using an original type cap with the radiator filled to just over the cores when cold? That almost always works well if the radiator is correct and in good condition, and it seems yours is since it cools well

before I built my overflow tank that is exactly how I would fill my radiator. About a half inch over the cores when it was cold. I built my overflow tank out of the 3-inch piece of aluminum tubing, about 2 ft long. It gave me adequate for the overflow, seems like it would puke out almost a quart and a half.

[FlatheadTed]

why the original radiators were only good to 4 lbs .
Also could be pressure on the spring in the carbon seal ,to much pressure you have a leaking pump ,